Add alerts for memcached

Change-Id: I23dcc01a6d243602039142008aa93bde0f5e88d4
diff --git a/metadata/service/support.yml b/metadata/service/support.yml
index 5acebbd..3e7214c 100644
--- a/metadata/service/support.yml
+++ b/metadata/service/support.yml
@@ -13,3 +13,5 @@
         enabled: true
       telegraf:
         enabled: true
+      prometheus:
+        enabled: true